"And what happens with the "Boris Continuum 3D Objects Unit - license" (which comes with the vegas 15 upgrade), when i upgrade to "vegas 16"?"

I think only official support can tell you what exactly the license terms are. My personal guess is:
Based on the prices (BCC 3D Objects Unit even is part of the Vegas Pro Edit Upgrade which is $199 and 3D Objects Unit usually is $299 alone) it looks like this may be a license which is coupled with this very Vegas Pro 15 license and which won't work within other Vegas Pro versions. Again: Just my guess.

If so - I don't understand why Magix/Vegas Creative Software does not make this clear on the website. I can't find any information about the license model for the added plug-ins.

"And what happens with the "Boris Continuum 3D Objects Unit - license" (which comes with the vegas 15 upgrade), when i upgrade to "vegas 16"?"

I think only official support can tell you what exactly the license terms are. My personal guess is:
Based on the prices (BCC 3D Objects Unit even is part of the Vegas Pro Edit Upgrade which is $199 and 3D Objects Unit usually is $299 alone) it looks like this may be a license which is coupled with this very Vegas Pro 15 license and which won't work within other Vegas Pro versions. Again: Just my guess.

If so - I don't understand why Magix/Vegas Creative Software does not make this clear on the website. I can't find any information about the license model for the added plug-ins.

I did send an email to the official support, Marco, 2 days ago...but did not get an answer untill this moment. Nor from NewblueFX.

If i only can use the plugin for 1 year (the estimated timespan before a new update arises)...Then it is useless to use them at all in projects...or you would have to start different vegasversions each time, which is to cumbersome.

Also paying them now at a discount with the new vegasversion and a secondtime for a full version, if it i would use them in fullversion...is paying twice...